READ: The Anthropocene

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For the first time in the history of life on Earth, a single species, humans, has gained the capacity to greatly change the entire biosphere.

Geologists have worked out a system of naming large segments of Earth's time. Thousands of years are called "epochs." Tens of millions of years are "periods." Hundreds of millions of years are "eras." The longest measurements of time are called "eons." Geologists call our current epoch the Holocene. It started about 10,000 years ago, when temperatures stabilized after the last ice age. The word Holocene comes from Greek roots: holo meaning "whole" and cene meaning "new." Hence, Holocene means "wholly new."

In 2000, a Nobel Prize-winning chemist suggested that we are in a new epoch—the Anthropocene. The chemist, Paul Crutzen, proposed that human domination has altered the planet greatly and thus brought on a new epoch. Anthropo is the Greek root for "human." The name Anthropocene has not been officially adopted, but many geologists have begun using it${}^1$‍.

But why should we care about this name change? This means that it's the first time scientists have seen one species, humans, having an impact that has greatly altered the planet. Unfortunately, these changes have been almost entirely negative.

What kind of evidence could demonstrate that humans have begun to dominate and alter the life systems of Earth? The most prominent answer is by now a familiar one: climate change${}^2$‍. Driven by an average rise in temperatures around the world of about 1 degree Celsius, a number of serious effects are now occurring. Plants and animals are moving northward. Glaciers are melting. Storms and droughts are getting more severe. Weather patterns are changing and global temperatures are rising. Behind these weather patterns are changes in the Earth's atmosphere that scientists can track over geologic time.

A tiny part of Earth's atmosphere is made up of "greenhouse gases." These gases hold in heat reflected from Earth and do not let it escape into space. One of these greenhouse gases is carbon dioxide (CO2). During the past million years, CO2 ranged from 180 parts per million (ppm) to 280 ppm—due to processes not affected by humans. Since the beginning of human agriculture, the atmospheric concentration of CO2 has risen from 280 ppm to the current (2017) level of 405 ppm${}^3$‍. This rise happened much faster than ever before. It was mostly due to humans burning fossil fuels in the last 250 years.

In order to keep our climate from devastatingly warming, leading scientists urge us to reduce the concentration of CO2 to 350 ppm. Because CO2 lingers in the atmosphere for thousands of years, the CO2 that has been put into the air in the 1900s continues to contribute to warming. If we are to curb that effect, scientists tell us that global emissions (release) of CO2 must be cut by 50 percent by 2030 and fall to net zero by the year 2050. However, from 2014-2016 worldwide emissions increased by 1.6 percent. In addition, the increase for 2018 was 2.7 percent. Emissions in both China and India rose by almost 5 percent and more than 6 percent respectively, reflecting the rate at which these countries' emissions continue to grow as they industrialize. The United States' emission increased by 2.5 percent. However, emissions in the European Union decreased by almost 1 percent. The United Nations Secretary General António Guterres issued a stark warning at the 24th annual U.N. climate conference in 2018 stating, "We are in trouble. We are in deep trouble with climate change…It is hard to overstate the urgency of our situation. Even as we witness devastating climate impacts causing havoc across the world, we are still not doing enough, nor moving fast enough, to prevent irreversible and catastrophic climate disruption" (Washington Post).

You might think that natural changes in climate occur slowly and gradually, but it doesn't always happen that way. Sometimes, like at the end of the last ice age, change speeds up because of feedback cycles. For example, when glaciers at the poles melt, there is less area of whiteness to reflect some of the Sun's heat back into space. Instead, the heat is absorbed into the land and water, warming it and causing more melting of the glaciers, which then reflect even less heat. The feedback cycle continues.

It's not only the atmosphere that has been changed by CO2 emissions. The chemistry of the oceans has changed as a significant amount of the CO2 in the air dissolves into the oceans. As more CO2 is absorbed into the oceans, it makes the water more acidic, endangering the life of creatures that form calcium shells that disintegrate under too much acid. Runoff from fertilizers and pesticides contributes as well. It causes strange accumulations of harmful algae, called blooms. Widespread overfishing threatens marine species worldwide. Our production and distribution of plastics is also affecting the oceans and the species that live in it. The effects of human use of fossil fuels in the creation of plastics is also a worrying concern. Both large and microscopic pieces of plastic as well as oil runoff and spills enter the waterways and become hazardous to life in our oceans, rivers, lakes, and streams.

More than just sea life is at risk. The biodiversity of all sectors of the planet is declining faster than usual. Reports put the present rate of decline as between a hundred and a thousand times the normal rate. Up to half of all species face extinction in the twenty-first century. Many biologists believe the current extinction, which is occurring right now, will rank as one of Earth's six major ones.

Another way that humans are changing Earth's systems lies in our ability to create artificial chemicals. These include drugs, pesticides, plastics, and synthetic fabrics. Earth is absorbing these chemicals, with unknown side effects.

Nuclear energy is another powerful force that humans have developed. The buildup of radiation in the environment from nuclear bomb testing and use as well as from nuclear energy waste and accidents has affected the Earth's environment. The United States first tested and then used nuclear bombs as weapons of war in 1945. A number of nations have performed similar tests in their quest to obtain nuclear weapons. In addition, increased levels of radiation on Earth have resulted from nuclear power waste and fallout from nuclear disasters at Three Mile Island (US), Chernobyl (Ukraine), and Fukushima (Japan). Exposure to radiation can damage or mutate the cells of all living organisms.

The evidence above comes from biologists and climate scientists. But geologists have a very specific way of determining historical periods. They look for evidence in the rocks, or at least in layers of mud that will become rock. And even in the mud they are finding evidence of environmental harm. Worldwide sediments contain radiation from atomic bomb testing in the 1960s. Similar evidence of chlorine from bomb testing and of mercury associated with the burning of coal also exists in ice-core samples. Environmental historians support the claims of geologists. Scholar John McNeill wrote an environmental history of the twentieth-century world called Something New Under the Sun. In it he asserts that "the human race, without intending anything of the sort, has undertaken a gigantic uncontrolled experiment on the Earth."

There are differing opinions about what these changes might bring and how humans might be able to overcome them. James Lovelock, an English scientist, believes that humans are no longer able to control change. He believes the planet will be returned to some kind of equilibrium, which may not support much human life. According to Lovelock, the best we can do is try to adapt to the changes.

Others believe humans are clever enough to find our way out of any tight spot. We can use our collective learning to create new ideas, new technologies, and new solutions. In fact, human communities have survived previous crises. Why can’t we do it again?

Geologists continue to debate other questions: When did the Anthropocene begin? How do we know when we have reached the critical point of human influence on the Earth? Just considering these questions has allowed scientists to examine contemporary change. Meanwhile, people have to face this decisive period in planetary history. Human decisions made in the near past and those made in the near future will determine the direction of life on our planet.

Many leading scientists and journalists believe that we have at most 10 years to change our destructive behavior and to implement new technologies. Otherwise, humans could face a breakdown in our planet’s life-support systems. It will take the commitment, innovation, and cooperation of a large portion of all humans on the planet to safely make these changes.

Cynthia Stokes Brown was an American educator-historian. Stokes Brown wrote Big History: From the Big Bang to the Present. Using the term big history, coined by David Christian at Macquarie University in Sydney, Australia, Stokes Brown told the whole story from the Big Bang to the present in simple, non-academic language to convey our common humanity and our connection to every other part of the natural world.